The present invention relates to a veneer lathe (peeling machine) for cutting (peeling) a veneer by making use of a cutting knife from a rotating log.
As disclosed in U.S. Pat. No. 4,219,060; U.S. Pat. No. 4,221,247; and Japanese Patent S59-45484, there is known a veneer lathe comprising a roller disposed substantially parallel with the linear cutting edge of the knife and provided with a large number of driving members which are arranged at intervals along the axial direction of the roller, each driving member being provided along the circumference thereof with a large number of piercing projections, and a guiding member for guiding a veneer that has been cut by the knife to run along the driving members.
The aforementioned conventional veneer lathe is constructed as shown in FIG. 13 illustrating a partial enlarged view thereof and also in FIG. 14 illustrating a partial cross-sectional view as it is viewed in the direction of the arrow from the dot and dash line Kxe2x80x94K in FIG. 13. By the way, a veneer 111 to be explained hereinafter is omitted in FIG. 14.
Referring to FIGS. 13 and 14, the veneer lathe comprises a cutting knife 103, and a roller disposed substantially parallel with the linear cutting edge of the knife 103 and provided with a large number of piercing rolls 105 each functioning as a driving member which are arranged, through the interposition of a ring-shaped spacer 106, at intervals along the axial direction of a rotary shaft 107 to be rotationally driven by a driving source (not shown), each piercing roller 105 being provided along the circumference thereof with a large number of piercing projections 105a, and both knife 103 and roller being mounted on a knife carriage 101. This roller is positioned so as to enable the piercing projections 105a to pierce not only the outer peripheral wall portion of a log 109 in the vicinity of the cutting edge of the knife 103 but also a portion of the veneer 111 which is located immediately after the cutting thereof during the cutting operation of the log 109.
In the space between neighboring piercing rolls 105, there is disposed a nose bar 113, upper end portion of which is fixed to a portion of the knife carriage 101 and the lower end of which is designed to be press-contacted with an outer peripheral wall portion of the log 109 which is located immediately before being cut by the cutting knife 103.
In conformity with each nose bar 113, a stripping member 115 having a stripping face 115a for separating the veneer 111 from the piercing projections 105a of piercing rolls 105 is attached to the knife carriage 101. Furthermore, a concaved member 101a and a guiding member, both of which are designed to guide the veneer 111 that has been cut by the cutting knife 103 to run along the piercing rolls 105, are attached to the knife carriage 101.
In this case, as explained hereinafter, the veneer 111 is completely press-contacted with the stripping face 115a of stripping member 115 so as to form slits 111a on front surface of the veneer 111, or the surface facing the stripping face 115a, and furthermore, for the purpose of enhancing the effect of flattening the veneer, the distance between the tip end of the piercing projections 105a and the concaved member 101a or the guiding member 117 is usually made smaller than the thickness of the veneer 111.
By making use of the veneer lathe having the aforementioned structure, the piercing rolls 105 is allowed to rotate and at the same time, the log 109 is allowed to rotate by means of a spindle (not shown) while controlling a synchronizing mechanism (not shown) in such a manner that the peripheral speed of the log 109 becomes always identical with the peripheral speed of the piercing rolls 105, under which conditions, the knife carriage 1 is moved at ratio of 3.5 mm per rotation of the log 109.
As a result, as shown in FIG. 13, the outer peripheral wall of the log 109 is permitted to be pierced by the piercing projections 105a of the piercing rolls 105 as shown in FIG. 13, thereby giving a rotational force to the log 109 also from the piercing rolls 105 and allowing the log 109 to be cut by the knife 103 with the peripheral surface of the log 109 being pressed by the chip 113a of nose bar 113, thus obtaining the veneer 111 having a thickness of 3.5 mm for instance.
In this case, the veneer 111 is pierced by the piercing projections 105a and allowed to move as guided by the concaved member 101a and the guiding member 117 to the stripping member 115, which enables the veneer 111 to be separated from the piercing projections 105a and bent to form slits 111a in the veneer 111. As a result, it is possible to obviate the generation of so-called curling phenomenon or a phenomenon of causing the veneer to be rounded into a cylindrical configuration, thus making it possible to obtain a flat veneer, which makes it easy to work the veneer in the following steps.
As explained above, the provision of these concaved member 101a, guiding member 117 and stripping member 115 is certainly important in the aforementioned veneer lathe. However, due to the piercing by the piercing projections 105a of piercing rolls 105, a large number of scars are caused to be formed on the front surface of the veneer 111.
As in a case where a face sheet to be employed as a front sheet of plywood for example is to be produced in the aforementioned veneer lathe, it is sometimes desired to obtain a veneer 111 having a flat front surface which is free from any pierced scar due to the piercing projections 105a of piercing rolls 105. According to the conventional veneer lathe however, even if the rotational axis 107 of the piercing rolls 105 is moved away from the log 109 from the state shown in FIG. 13, i.e. moved in the rightward direction in FIG. 13, thus separating the piercing projections 105a from the log 109 as shown in FIG. 15, it is impossible, due to fact that the concaved member 101a constituting a guide member and the guiding member 117 are located along the transferring direction of veneer, to avoid the pierced scar by the piercing rolls 105 from being formed in the front surface of the veneer 111.
Namely, in the state shown in FIG. 15, the log 109 can be prevented from being pierced by the piercing projections 105a. However, since the distance between the tip end of the piercing projections 105a of the piercing rolls 105 and the concaved member 101a or the guiding member 117 cannot be changed substantially, the veneer 111 is caused to be pierced by the piercing projections 105a as it passes through the concaved member 101a or the guiding member 117, thereby leaving pierced scars on the surface of the veneer 111.
The object of the present invention is to provide a veneer lathe which is capable of producing a veneer which is free from the aforementioned pierced scars in spite of facts that the veneer lathe is provided with a driving member such as the aforementioned piercing rolls 105 and with a guiding member such as the concaved member 101a or the guiding member 117.
Namely, the veneer lathe according to the present invention comprises; a knife for cutting a log; a roller disposed substantially parallel with the linear cutting edge of the knife and provided with a large number of driving members which are arranged at intervals along the axial direction of the roller, each driving member being provided along the circumference thereof with a large number of piercing projections; a driving mechanism attached to the roller; a pressure member disposed at a location which enables the pressure member to press-contact with the outer peripheral wall of the log through a plurality of spaces formed between said driving members neighboring to each other of the roller; a guiding member for guiding a veneer which is cut by means of said knife to move along said driving members; a knife carriage for mounting thereon said knife, said roller, said driving mechanism, said pressure member and said guiding member; a spindle rotatably supporting a log; and a driving for rotating said spindle; wherein said roller is enabled to take a first position wherein said piercing projections of the driving member is enabled to pierce not only the outer peripheral wall portion of a log in the vicinity of said cutting edge of said knife but also a portion of the veneer which is cut by said cutting knife and is not yet passed through said guiding member, as well as to take a second position wherein said piercing projections of the driving member is not allowed to contact with not only the outer peripheral wall portion of the log but also said portion of the veneer or wherein the tip ends of said piercing projections are contacted only with the outer peripheral wall portion of the log in the vicinity of said cutting edge, said rollers being designed to be fixed at said first position or at said second position.
According to the veneer lathe of the present invention, the roller is kept at the first position on the occasion of ordinary cutting operation. However, when it is desired to obtain a veneer having a flat smooth surface as in the case where a face sheet to be employed as a front sheet of plywood is desired to obtain, the roller is moved from the first position to the second position. As a result, it becomes possible to avoid the veneer to be cut from being pierced by the piercing projections, thus obtaining a veneer free from any piercing scar.
Although there is not any particular limitation regarding the means for moving the roller from the first position to the second position and vice versa, and for fixing the roller at these positions, the means should preferably be constituted by a first reciprocating member mounted on the knife carriage for enabling the roller to be reciprocatively moved to take a position permitting the piercing projections to pierce the outer periphery of log in the vicinity of the cutting edge of the knife or to take a position where the piercing projections are kept away from the outer periphery of log, and by a second reciprocating member mounted on the knife carriage for enabling the roller to be reciprocatively moved to take a position where a distance between the tip end of the piercing projections and the guiding member located in the vicinity of the cutting edge of the knife and in the running direction of the log is smaller than the thickness of the veneer being cut, and to take a position where said distance is larger than the thickness of the veneer being cut.
As for the first reciprocating member, it may be constituted by a reciprocating member which enables the roller to be reciprocatively moved to take a position permitting the piercing projections to pierce the outer periphery of log in the vicinity of the cutting edge of the knife or to take a position where the tip ends of piercing projections are allowed to contact with the outer periphery of log in the vicinity of the cutting edge.
In this veneer lathe, the first reciprocating member may be constituted by an air cylinder. Further, the second reciprocating member may be constituted by an eccentric cam, wherein the roller is rotatably secured to a lower end portion of an arm which is enabled to be moved to take, through the rotation of this eccentric cam, a position which is close to the guiding member or a position which is away from the guiding member.
Alternatively, the first reciprocating member may be constituted by a reciprocating member which enables the roller to be reciprocatively moved to take a position permitting the piercing projections to pierce the outer periphery of log in the vicinity of the cutting edge of the knife, to take a position where the tip ends of piercing projections are allowed to contact with the outer periphery of log in the vicinity of the cutting edge, or to take a position where the piercing projections are kept away from the outer periphery of log.
In this veneer lathe, the first reciprocating member may be constituted by an air cylinder provided with an intermediate stopping mechanism.